This invention relates to gasified liquid fuel feeding devices, and more particularly to a gasified liquid fuel feeding device operable to deliver gasified liquid fuel for mixture with air to a burner for combustion.
In combustion apparatus of the type to which the present invention relates, liquid fuel is delivered to a gasifying device where it is heated to the point of gasification. The gasified fuel is then delivered to a mixing tube where it is mixed with air and supplied to a burner. An ignition plug ignites the mixture at the burner.
Emission of the gasified fuel from the gasifier to the burner may be controlled by a discharge nozzle having a retractable valve needle cooperable therewith. In such constructions, it is known to utilize a solenoid which, when energized, retracts the valve needle and opens the nozzle. Also in such constructions, the valve needle is operated to close the nozzle by a compression spring upon deenergization of the solenoid. A typical construction of this type is disclosed in Japanese Laid-open Patent Application No. SHO 50-120040.
One of the problems in devices of this type is that soot or tar or other impurities in the liquid fuel is deposited on the nozzle and the valve needle particularly after prolonged use. This can cause the valve needle to stick to the nozzle in the closed position making it difficult to retract the valve needle and open the nozzle. Similarily, such deposits on the nozzle and the valve needle can make it difficult for the valve needle to return to the closed position upon deenergization of the solenoid.
It is necessary, therefore, that the solenoid be capable of exerting sufficient force on the valve needle to overcome the forces developed by a sticking valve needle and nozzle. It is also necessary that the solenoid be capable of overcoming the force of the compression spring which must be strong enough to cause the valve needle to close the nozzle in spite of soot or tar or impurities which may be on the valve needle or nozzle.
It will be appreciated that the force developed by a given solenoid is dependent upon its size and upon the current used to energize the solenoid. A large sized solenoid is undesirable for reasons of its dimensions, its cost, and its power consumption.
Also, the heat generated in a solenoid is a function of the current in the solenoid. Because the solenoid in gasifier devices of the type to which the present invention relates is heated by thermal conduction from the gasifier which necessarily is maintained at a high temperature, it is important that the current and resulting heat generated in the solenoid be minimized.
The present invention overcomes the aforementioned problems by providing a solenoid control circuit which is operable to provide high electric current initially for opening the nozzle, and which thereafter provides a relatively weak current which is sufficient to maintain the nozzle open.
Further objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the objects and in accordance with the purposes of the invention, as embodied and described herein, this invention is directed to a gasified liquid fuel combustion apparatus in which a gasified fuel is emitted from a nozzle having a valve needle actuated by a solenoid and is mixed with combustion air and the fuel-air gaseous mixture thus obtained is supplied to a burner for combustion, comprising a power supply; a solenoid control circuit including a timer circuit adapted to operate upon closing of a power switch; a contact switch adapted to open in response to the timer circuit, a voltage reducing transformer powered from said power supply through the power switch; a first rectifying circuit and a second rectifying circuit connected to the solenoid; the first rectifying circuit receiving from the power supply through the contact switch a voltage higher than but of the same phase as the voltage supplied from the power supply to the second rectifying circuit; the second rectifying circuit receiving a lower voltage from the secondary side of the voltage reducing transformer; the first and second rectifying circuits being connected to a common output line to provide a high DC output voltage until the contact switch is opened but to provide a low DC output voltage thereafter, thereby controlling the solenoid control circuit.
In another aspect, this invention relates to a gasified liquid fuel combustion apparatus in which a gasified fuel is emitted from a nozzle having a needle valve actuated by a solenoid and is mixed with air and supplied to a burner for combustion, a control circuit for the solenoid comprising a power supply; a solenoid; a power switch; a timer circuit operable upon closing of the power switch; a normally closed contact switch connected to the timer circuit and operable to open after a predetermined time following closing of the power switch determined by the timer circuit; a voltage reducing transformer connected to the power supply when the power switch is closed; a first rectifying circuit and a second rectifying circuit, the first rectifying circuit receiving a voltage higher than but of the same phase as the voltage supplied by the power supply to the second rectifying circuit when the contact switch is closed; the second rectifying circuit receiving a lower voltage from the secondary side of the voltage reducing transformer; the first and second rectifying circuits being connected to a common line to provide a high DC output voltage to the solenoid when the contact switch is closed at a low DC output voltage to the solenoid when the contact switch is opened in response to the timer circuit.
The accompanying drawings which are incorporated in and constitute part of this specification, illustrate embodiments of this invention and, together with description, serve to explain the principle of the invention.